Abstract
A new optical probe technique using a laser-trapped erbium oxide nanoparticle (size similar to 150 nm) is introduced that can measure absolute temperature with a spatial resolution on the size of the trapped nanoparticle. This technique (scanning optical probe thermometry) is used to collect a thermal image of a gold nanodot prepared with hole-mask colloidal lithography. A convolution analysis of the thermal profile shows that the point spread function of our measurement is a Gaussian with a FWHM of 165 nm. We attribute the width of this function to clustering of Er2O3 nanoparticles in solution. The scanning optical probe thermometer is used to measure the temperature where vapor nucleation occurs in degassed water (555 K), confirming that a nanoscale object heated in water will superheat the surrounding water to the spinodal decomposition temperature. Subsequently, the temperature inside the vapor bubble rises to the melting point of the gold nanostructure (similar to 1300) where a temperature plateau is observed. The rise in temperature is attributed to inhibition of thermal transfer to the surrounding liquid by the thermal insulating vapor cocoon.